NOTE: These are the main Borderlands 2 cheats that are usually applied by pressing down the right key combination. Please find the instructions on how to use these cheats below.

Steam Achievements
A Road Less Traveled: Completed the mission "The Road To Sanctuary"
Always Improving: Reached level 25
An Angel's Wish: Completed the mission "Where Angels Fear To Tread"
An Old Flame: Completed the mission "Hunting The Firehawk"
Arctic Explorer: Discovered all named locations in Three Horns, Tundra Express, and Frostburn Canyon
Better Than Money: Purchased 5 items from the black market
Better Than You Were: Reached level 10
Blight Explorer: Discovered all named locations in Eridium Blight, Arid Nexus, and Sawtooth Cauldron
Bombs Away: Completed the mission "Toil And Trouble"
Bounty Hunter: Completed 20 side missions
Build Buster: Killed a Constructor without it ever building another bot
Can See My House From Here: Completed the mission "Bright Lights, Flying City"
Capped Out...For Now: Reached level 50
Challenge Accepted: Completed level 1 of all non-level-specific challenges with a single character
Cool Story, Bro: Defeated Jack
Cute Loot: Killed a Chubby
Decked Out: Had Purple-rated gear or better equipped in every slot
Definitely An Italian Plumber: Killed Donkey Mong
Did It All: Completed all side missions
Dragon Slayer: Completed the mission "Best Minion Ever"
Farewell, Old Girl: Completed the mission "Wildlife Preservation"
Feels Like The First Time: Opened the chest at the bus stop in Fyrestone
First One's Free: Completed the mission "My First Gun"
Friendship Rules: Revived someone from "Fight for Your Life!" that is on your friends list
Goliath, Meet David: Allowed a Goliath to level up four times before killing him
Got The Band Back Together: Completed the mission "The Once and Future Slab"
High-Flying Hurler: Killed a flying enemy with a thrown Tediore weapon
Highlands Explorer: Discovered all named locations in The Highlands, Thousand Cuts, and Wildlife Exploitation Preserve
How Do I Look?: Unlocked 10 customization items
Identity Theft: Completed the mission "The Man Who Would Be Jack"
Knowing Is Half The Battle: Completed the mission "Data Mining"
New In Town: Completed the mission "Plan B"
No Man Left Behind: Completed the mission "A Dam Fine Rescue"
Not Quite Dead: Reached level 5
Phased and Confused: Phaselocked 100 enemies
Sabre Rattler: Killed 100 enemies with the Sabre turret
Sky's The Limit: Completed the mission "Rising Action"
So Much Blood!: Gunzerked continuously for 90 seconds
Sugar Daddy: Tipped Moxxi $10,000
Thresher Thrashed: Defeated Terramorphous the Invincible
Token Gesture: Redeemed 25 tokens
Tribute To A Vault Hunter: Got an item from Michael Mamaril
Unseen Predator: Remained in Zero's Deception mode for ten seconds straight
Up High, Down Low: Gave Claptrap a high five
Urban Explorer: Discovered all named locations in Sanctuary, Opportunity, and Lynchwood
Well That Was Easy: Completed the mission "Shoot This Guy in the Face"
Went Five Rounds: Completed Round 5 of any Circle of Slaughter
What does it mean?: I can't even capture it on my camera
Wilhelm Screamed: Completed the mission "A Train To Catch"
World Traveler: Discovered all named locations

Infinite Eridium
Enter the 'Three Horns Valley' then head northwest to the Bloodshot hideout and kill the 'Bad Maw' boss. As soon as you take out Bad Maw, collect the Eridium, which he leaves behind. Once you enter the Bloodshot Stronghold head to the main menu and select 'Save and Quit'. Continue the game, go back to Three Horns Valley, deal with Bad Maw once more and grab additional Eridium. You can do this as often as you wish.True Vault Hunter Mode
Complete Normal difficulty story mode.

Minecraft enemies and outfit
In the Caustic Caverns underneath Sanctuary, near the furthest edge, there is a shallow incline. If you go along the left-most cliff beside the incline, you will find Minecraft blocks. Breaking them will lead into an area with creepers from the Minecraft games, a golden ore block with a normal outfit, and a special outfit for defeating the creepers.

Carry one more item in your backpack
You must have 2 class mods for this to work. Once your backpack is full, switch your currently equipped class mod for another one in your backpack (you can then re-equip your original class mod after you've done this). Then exit the backpack menu and you can now pick up one more item and have a backpack with 28 items in it instead of maximum 27.